I have my 105 amp single wire alternator on the drivers side of the motor, I have run a #6AWG back to the firewall then down the fender, across the rad support and then on the junction block. Total lenght is about 12 feet. My question is should I redo it and just run it across the front of the motor and straight to the junction block? The total length wil be less than 4 feet
Are there any issues with this routing? Is heat an issue? Or should I just leave well enough alone.

I'd run it straight to the battery unless you've upgraded the factory wiring. I also put a 100A fusible link in mine.

you want to keep the length as close to 12 feet as possible to provide some voltage drop so the alt can react to the load on your system and maintain a charging voltage of 14 volts, although this is very hard to do with a single wire alt as the voltage sensing that changes the charging rate is created in the alt itself, instead of at the point where your accessories are powered from. A single wire alt will never work as well as one with remote voltage sensing capability. Check out this link and it will explain why (you might want to read all of their tech articles as well... very good info)
http://www.madelectrical.com/electricaltech/onewire-threewire.shtml

You've done fine with wire replacement so far. Continue to replace the wire from the junction block to the positive battery clamp.

You've done fine with wire replacement so far. Continue to replace the wire from the junction block to the positive battery clamp.

That is done as well, #6 awg from the junction to the Battery, Thanks